Method and apparatus for forming a cabochon

ABSTRACT

A cabochon is formed by rotating a gemstone workpiece about a rotational axis while contacting it with an abrasive surface, moving the workpiece and the rotational axis in a radial path in response to its rotational movement to change the lateral position of the rotational axis in response to the angular displacement of the workpiece during its rotation, and swinging the rotational axis with respect to the abrasive surface, the swing axis lying normal both to the rotational axis and to the radial movement of the rotational axis.

United States Patent 91 Moeller Sept. 10, 1974 METHOD AND APPARATUS FORFORMING A CABOCl-ION [76] Inventor: John T. Moeller, 2858 State Rd.

590, Clearwater, Fla. 33515 22 Filed: July 2,1973

211 Appl. No.: 376,100

[52] U.S. Cl. 51/127, 51/101 R, 51/229, 51/283 [51] Int. Cl B24b 7/00,B24b 9/16, B24b 19/00 [58] Field of Search 51/100, 101 R, 121, 127,51/229, 283, 97

[56] References Cited UNITED STATES PATENTS 1,998,642 4/1935 Smith51/229 3,041,789 7/1962 Cretin-Maitenaz 3,568,369 3/1969 Marshall 51/97R 3,673,742 7/1972 Colbaugh 51/101 R Primary Examiner-Othell M. SimpsonAttorney, Agent, or FirmBrowne, Beveridge, DeGrandi & Kline 5 7 ABSTRACTA cabochon is formed by rotating a gemstone'workpiece about a rotationalaxis while contacting it with an abrasive surface, moving the workpieceand the rotational axis in a radial path in response to its rotationalmovement to change the lateral position of the rotational axis inresponse to the angular displacement of the workpiece during itsrotation, and swinging the rotational axis with respect to the abrasivesurface, the swing axis lying normal both to the rotational axis and tothe radial movement of the rotational axis.

11 Claims, 6 Drawing Figures SHEET 2 0f 3 PAIENTEB SEN man HHI' I SHEET3 BF .3

PAIEMEB SEP 1 01914 METHOD AND APPARATUS FOR FORMING A CABOCHON Thisinvention relates to a method and apparatus for making a cabochon from arough cut or uncut natural or synthetic stone. The resulting product isa cabochon gemstone provided with an unfaceted convex face.

Heretofore, cabochons have been made either manually or by specializedapparatus, typical examples of which in recent years are exemplified byUS. Pat. Nos. 3,279,127, 3,568,369 and 3,673,742. The latter of thesepatents bears a number of similarities to the cabochon grinder disclosedherein, but it has severe limitations in that it requires a speciallyshaped abrasive surface which is incapable of making cabochons withvarying degrees of curvature.

The present invention involves a relatively uncomplicated method andapparatus which is capable of making a variety of shapes and sizes ofcabochons in an efficient and expeditious manner.

The invention is performed by the following steps and for means forperforming these steps: supporting a workpiece for rotational movementabout a rotational axis, moving the workpiece and the rotational axis ina radial path which lies radial to the rotational axis, the lattermovement being in response to rotational movement so that the positionof the rotational axis along the radial path is dependent upon theangular displacement of the workpiece, and providing relative swingingmovement between the abrasive surface and the rotational axis, thisswinging movement being about a swing axis which is normal both to therotational axis and to the radial path.

Although the invention is capable of being performed by a wide varietyof devices, a preferred form thereof is described herein for purposes ofillustration.

Referring now, to the drawings, FIG. 1 is a diagrammatic perspectiveview which illustrates the various paths of movement of the shaft whichsupports the workpiece.

FIG. 2 is a plan view corresponding to FIG. 1, also showing the extentof swinging movement of the workpiece-supporting shaft.

FIG. 3 is a plan view of a preferred form of apparatus embodying theconcepts of the invention.

FIG. 4 is a sectional view of the apparatus as seen along the line 44 inFIG. 3.

FIG. 5 is a sectional view of the apparatus as seen along the line 55 inFIG. 3.

FIG. 6 is a sectional view showing the drive means for swinging theworkpiece-supporting shaft as seen along the line 66 in FIG. 3.

The basic concept of the invention is depicted in FIGS. 1 and 2 whichillustrate an abrasive wheel 2 supported on a driven shaft 4 andprovided with a flat abrasive surface 6 for grinding or polishing thematerial from which the cabochon is formed. The workpiece itself is anatural or synthetic stone 8 supported in a conventional manner on a dopshaft 10 and held in contact with the abrasive surface 6 of the wheel 2.During the forming of the cabochon, the abrasive surface 6 of the wheel2 stays in a same plane, and the dop shaft 10 is manipulated in a mannerwhich will result in the formation of the cabochon-shaped surface on thefinal product.

There are several movements of the dop shaft 10 which are compounded toachieve the desired results.

The shaft 10 rotates about its own longitudinal axis as indicated by thearrow 12. It also has a translatory movement in a path 14 which isradial with respect to the axis of dop shaft 10. This radial movement isimparted to the shaft by a cam, described below, which moves the shaftin the direction of arrow 14 in response to shaft rotation so that theposition of the longitudinal axis of the shaft changes with and isdependent upon its angular displacement during rotation.

The third aspect of movement is a swinging movement of the dop shaft 10about the swing axis AA, oriented normal to the longitudinal axis andthe radial path of the dop shaft 10. This latter movement is shown bythe arrow 16, and it may be accomplished by swinging the abrasive wheel2 instead of the dop shaft 10. The two extreme positions of the shaftduring its swinging movement are seen in FIG. 2 where the swing axisappears as a point and is designated A.

In addition to the movements illustrated in FIGS. 1 and 2, the preferredapparatus is provided with adjustment means which permits bothlongitudinal and transverse shifting of the dop shaft 10 with respect tothe swing axis AA. Such adjustments permit the operator to change theshape and curvature of the final product produced by performing thesteps illustrated in FIGS. 1 and 2.

A preferred apparatus for performing the invention is illustrated inFIGS. 3-6. In these drawings, it will be seen that the rotationalmovement, identified by arrow 12 in FIG. 1, is accomplished byrotationally supporting the dop shaft 10 by the elements in a housing26. The shaft may be turned manually by means of the crank arm 22 havinga handle 24, or it may be accomplished by a motor having suitablereduction gearing for rotating the shaft.

The dop shaft 10 projects from a housing 26 which encloses the means forrotationally supporting it and moving it along the path designated 14 inFIG. 1. As best illustrated in FIG. 5, the shaft 10 has an ellipticalcam 28 affixed thereto for concurrent rotation by a set screw. Theapparatus may be provided with a number of cams 28 having various sizesand shapes, which may be interchanged for making cabochons of differentshapes. Dust seals 18 and 20 are attached to the dop shaft 10 andprevent abrasive particles and other foreign matter from entering thehousing 26.

The contoured face of the cam 28 is in engagement with a cam follower 30which is rotatably mounted on a shaft 32 provided with reduced endportions 34 and 36 which seat within apertures on opposed walls of thehousing. As the cam rotates, its contact with the cam follower 30 willcause it to reciprocate in the direction of the arrow 14. The shaft 10is held at a constant orientation with respect to the housing 26 and incontinuous engagement with the cam follower 30 by means of the sliderblock 38 which is also positioned in the housing 26. The slider block 38is positively biased against spaced apart portions of the dop shaft 10by a spring 40 which has one end received in a recess 42 in the sliderblock and its other end positioned in a retainer 44 at the end of anadjustment screw 46 which is threadedly mounted in the end wall of thehousing 26. Of course, rotation of the adjustment screw 46 will changethe compression of the spring 40 and affect the force exerted by thespring 40 against the slider block 38 and ultimately on the shaft 10. Asseen in FIG. 3, the slider block 38 has a groove 48 for accommodatingthe cam 28 without contacting it. On opposite sides of the groove, theslider block has V-shaped recesses 50 best shown in FIG. 5 forcontacting the shaft and serving as bearing surfaces. The spacedrelationship of the two V- shaped recesses maintains the dop shaft 10 ata constant orientation with respect to the housing 26.

The swinging movement of the dop shaft about the axis AA is achieved bymounting the housing 26 on a support structure which is swingablymounted with respect to the abrasive surface. As seen in FIG. 4, thesupport structure is affixed by a set screw 52 to a shaft 54 which hason its lower end a gear segment 56. The shaft 54 pivots in a bore in thecenter of the platform 58 of the apparatus. The platform 58 is heldabove the supporting surface by spaced apart leg flanges 60 and 62. Onthe underside of the platform 58, there are a pair of depending supportbrackets 64 and 66 which, as shown in FIG. 6, support the shaft 68 of alead screw 70 which meshes with the gear segment 56 to rotate the dopshaft assembly. The shaft 68 may be rotated manually by a handle 72, butit preferably is operated by a motor having suitable reducing gearingfor slowly swinging the dop shaft assembly about the axis AA.

The drive motor 76 for the abrasive wheel 2 is supported on the platform58 by the motor support bracket 74. As seen in FIG. 3, the motor shaft 4extends through the bracket 74 and connects to the rear face of theabrasive wheel 2. It is desirable to mount the abrasive wheel 2 on theshaft 4 in a manner which permits adjustment in the spacing between theabrasive surface 6 and the axis AA, such adjustment providing thedesired initial positioning of the abrasive surface with respect to theaxis of the dop shaft 10. This movement may also be provided by mountingthe motor support bracket 74 for adjustable movement or by moving theaxis AA toward the abrasive surface 6.

A number of factors will affect the shape of the cabochon producedaccording to the invention. The shape of the cam 28 is determinative ofthe shape of the peripheral outline of the cabochon which will begeometrically similar thereto. Another factor will be the longitudinalposition of the dop shaft 10 with respect to the swing axis AA, inasmuchas the curvature of the convex face of the cabochon will be greater ifit is positioned closer to the axis AA. Further, the position of theswing axis AA with respect to the translatory movement of the dop shaft10 will affect its shape and will require adjustment, especially onoccasions when the shaft-moving cam 28 is replaced with a cam of adifferent size. In order to permit these adjustments, a pair of slidecarriages are interposed between the housing 26 and the pivot shaft 54for the dop shaft assembly.

The swinging base member 78, best seen in FIGS. 4 and 5, rests on theupper surface of the platform 58 and, as previously described, isswingable with respect thereto. The swinging base 78 has a dovetailslide track open to its upper surface for slidably receiving a dovetailslide 80 which is attached to a sliding carriage 82. Movement of thedovetail slide 80 in the swinging base 78 is in the direction indicatedby the arrow 84 in FIG. 5. Such movement is produced by a lead screw 86which is engaged in a threaded aperture in a depending projection 90 ofthe dovetail slide 80. The lead screw 6 86 is rotationally mounted andlongitudinally affixed to the swinging base 78 by means of a bearingassembly 92. Rotation of the lead screw 86 is produced by turning theadjustment wheel 94 by means of the crank handle 96.

Adjustable movement of the dop shaft 10 in a direction parallel to itslongitudinal axis is made possible by mounting the housing 26 on adovetail slide 98 so that the housing 26 serves as an upper carriage.This dovetail slide 98 is received by a dovetail groove in the lowercarriage 82, the slide 98 having a depending flange 100 which has athreaded aperture for receiving the threaded adjustment shaft 102 bestshown in FIG. 4. The shaft 102 is attached to the lower sliding carriage82 by a bearing assembly 104 which permits the shaft 102 to rotate butprevents if from moving along its own longitudinal axis. The lead screwshaft 102 may be manually rotated by a crank handle 106 on theadjustment wheel 108. Of course, such rotation will result inlongitudinal movement of the dop shaft so as to change the distancebetween the surface of the workpiece and the swing axis AA. As thisdistance increases, the radius of the arc of curvature of the cabochonwill be increased.

The operation of the disclosed apparatus will be evident from theforegoing description. A workpiece is mounted on the dop shaft 10 andthe abrasive surface 6 is brought into contact with the cabochon. Theabrasive surface is rotated and the dop shaft is rotated, the latterrotation serving also to move the dop shaft in a radial path 14 underthe influence of the attached cam 28 which operates against thestationary cam follower 30. Concurrently, and at a slow rate, the entiredop shaft assembly swings about the axis AA until the dop shaft is at aposition normal to the abrasive surface as is illustrated in brokenlines in FIG. 2. At this point, the cabochon will be complete, havingbeen made in a relatively short period of time and withoutimperfections.

Those skilled in the art will realize that there are a great number ofways which the invention may be performed, and that the disclosedapparatus is merely exemplary of these. Therefore, it is emphasized thatthe invention is not limited only to the single embodiment disclosedhereinabove, but extends to encompass the modifications and variationsthereto which fall within the spirit of the following claims.

I claim:

1. Lapidary apparatus for use in shaping a gemstone workpiece into acabochon, comprising,

a shaft for supporting a workpiece,

said shaft being rotatable about its longitudinal axis,

means for moving the shaft in a radial path in response to its rotationso that the position of its longitudinal axis changes with and isdependent upon its angular displacement during rotation, abrasive meanshaving an abrasive surface for contacting a workpiece supported on theshaft, and

means for providing about a swing axis relative swinging movementbetween the longitudinal axis and the abrasive surface of the abrasivemeans, said swing axis lying normal both to the longitudinal axis and tothe radial path of the shaft.

2. The apparatus of claim 1 having means for adjusting the location ofthe shaft to vary the position of the workpiece with respect to theswing axis.

3. The apparatus of claim 2 wherein the means for adjusting the locationof the shaft includes a pair of carriages slidable in mutuallyperpendicular directions which lie perpendicular to the swing axis.

4. The apparatus of claim 1 wherein the means for moving the shaft in aradial path includes a cam connected to and rotatable with the shaft,and cam follower means engaged against the cam to move the cam and theshaft radially upon rotation of the shaft.

5. The apparatus of claim 1 wherein said swing axis is substantiallyperpendicular to the radial path and to the longitudinal axis of theshaft.

6. The apparatus of claim 5 having means for adjusting the location ofthe shaft to vary the position of the workpiece with respect to theswing axis.

7. The apparatus of claim 6 wherein the means for adjusting the locationof the shaft includes a pair of carriages slidable in mutuallyperpendicular directions which lie perpendicular to the swing axis.

8. The apparatus of claim 6 wherein the means for moving the shaft in aradial path includes a cam connected to and rotatable with the shaft,and cam follower means engaged against the cam to move the cam and theshaft radially upon rotation of the shaft.

9. The apparatus of claim 8 wherein the means for adjusting the locationof the shaft includes a pair of carriages slidable in mutuallyperpendicular directions which lie perpendicular to the swing axis.

10. Apparatus for making a cabochon, comprising, an abrasive surface,

means for supporting a workpiece for rotational movement about arotational axis,

means for moving the workpiece and the rotational axis in a path lyingradial to the rotational axis in response to said rotational movement sothat the position of the rotational axis along said path is dependentupon the angular displacement of the workpiece,

means providing for relative swinging movement between the abrasivesurface and the rotational axis, said relative swinging movement beingabout a swing axis which is normal both to the rotational axis and tosaid path.

11. A method of making a cabochon, comprising the steps of contacting aworkpiece with an abrasive surface while simultaneously doing thefollowing:

rotating the workpiece about a rotational axis,

moving the rotational axis in a path lying radial to the rotationalaxis, said movement being in response to rotation of the workpiece sothat the lateral position of the rotational axis along said path isdependent upon the angular displacement of the workpiece,

relatively swinging the abrasive surface and the rotational axis, saidswinging occurring about a swing axis which is normal both to therotational axis and to said path.

1. Lapidary apparatus for use in shaping a gemstone workpiece into acabochon, comprising, a shaft for supporting a workpiece, said shaftbeing rotatable about its longitudinal axis, means for moving the shaftin a radial path in response to its rotation so that the position of itslongitudinal axis changes with and is dependent upon its angulardisplacement during rotation, abrasive means having an abrasive surfacefor contacting a workpiece supported on the shaft, and means forproviding about a swing axis relative swinging movement between thelongitudinal axis and the abrasive surface of the abrasive means, saidswing axis lying normal both to the longitudinal axis and to the radialpath of the shaft.
 2. The apparatus of claim 1 having means foradjusting the location of the shaft to vary the position of theworkpiece with respect to the swing axis.
 3. The apparatus of claim 2wherein the means for adjusting the location of the shaft includes apair of carriages slidable in mutually perpendicular directions whichlie perpendicular to the swing axis.
 4. The apparatus of claim 1 whereinthe means for moving the shaft in a radial path includes a cam connectedto and rotatable with the shaft, and cam follower means engaged againstthe cam to move the cam and the shaft radially upon rotation of theshaft.
 5. The apparatus of claim 1 wherein said swing axis issubstantially perpendicular to the radial path and to the longitudinalaxis of the shaft.
 6. The apparatus of claim 5 having means foradjusting the location of the shaft to vary the position of theworkpiece with respect to the swing axis.
 7. The apparatus of claim 6wherein the means for adjusting the location of the shaft includes apair of carriages slidable in mutually perpendicular directions whichlie perpendicular to the swing axis.
 8. The apparatus of claim 6 whereinthe means for moving the shaft in a radial path includes a cam connectedto and rotatable with the shaft, and cam follower means engaged againstthe cam to move the cam and the shaft radially upon rotation of theshaft.
 9. The apparatus of claim 8 wherein the means for adjusting thelocation of the shaft includes a pair of carriages slidable in mutuallyperpendicular directions which lie perpendicular to thE swing axis. 10.Apparatus for making a cabochon, comprising, an abrasive surface, meansfor supporting a workpiece for rotational movement about a rotationalaxis, means for moving the workpiece and the rotational axis in a pathlying radial to the rotational axis in response to said rotationalmovement so that the position of the rotational axis along said path isdependent upon the angular displacement of the workpiece, meansproviding for relative swinging movement between the abrasive surfaceand the rotational axis, said relative swinging movement being about aswing axis which is normal both to the rotational axis and to said path.11. A method of making a cabochon, comprising the steps of contacting aworkpiece with an abrasive surface while simultaneously doing thefollowing: rotating the workpiece about a rotational axis, moving therotational axis in a path lying radial to the rotational axis, saidmovement being in response to rotation of the workpiece so that thelateral position of the rotational axis along said path is dependentupon the angular displacement of the workpiece, relatively swinging theabrasive surface and the rotational axis, said swinging occurring abouta swing axis which is normal both to the rotational axis and to saidpath.